Currently there are a number of different methods being used by dentists to create dental impressions which are ultimately used for the manufacture of crowns, veneers, and bridges.
For example a crown is a type of dental restoration which completely caps and encircles the tooth or dental implant. They are typically bonded to the tooth using a dental cement and are usually fabricated outside of the mouth in order that they can be made of strong material such as gold or ceramics.
The most common method of crowning a tooth usually involves a dental impression of a prepared tooth by a dentist for fabrication of the crown outside of the mouth. The crown can then be inserted at a subsequent dental appointment. Naturally the tooth to restoration margin is an unsightly thing to have exposed on the visible surface of the tooth when the tooth is positioned in the aesthetic zone of a smile. The dentist would like to place the margin as far toward the gum line as possible and even below the gum line.
In order to obtain impressions below the gum line typically a gingival retraction cord is placed around the tooth at the sulcus in order to push the gum away from the margin of the tooth at the gingival sulcus. In this manner it is possible to take a dental impression which extends below the gum line.
The difficulties with this technique are that there is a lot of trauma and damage to the gum at the gingival sulcus interface which usually results in bleeding during the procedure.
The blood and other fluids interfere with the impression material that is being used when making the impressions to have a crown manufactured.
Typically a vinyl polysiloxane impression material is used to take the impression of the prepared tooth. Typically one impression is taken and sent to the laboratory for manufacture of the crown.
Unfortunately there is variation amongst dental offices and the materials that they are using. Some dental office prefer to use a heavy impression material whereas other dental offices prefer to use a more light body meaning less viscous impression material. Some dental offices prefer to use a hydrophilic whereas other dental offices do not prefer hydrophilic materials. Some dental offices prefer to use triple trays as they are known in the industry for making an impression whereas other dental offices prefer other tray configurations.
So there is a great deal of inconsistency among dental offices which results in inconsistent accuracy of the impressions which the laboratory eventually has to deal with.
As a result there is a large degree of scrap in the manufacture of crowns which do not fit or require a lot of rework on the part of the dentist in order to make them fit properly onto the prepared tooth.
Other systems have also been unsuccessfully suggested, such as that described in U.S. Pat. No. 6,116,905 titled METHOD OF TAKING DENTAL IMPRESSIONS invented by Jeffrey C. Hoos. None of these other systems utilize hydraulic pressure to move the sulcus or apply impression material directly to the prepared tooth.
Therefore there is a need for a method and system of making dental impressions which provides for a uniform and reproducible dental impression which can be used by the laboratory to produce a uniform and consistent crown quality.